Scientists aboard NOAA Ship Oscar Dyson are aiming to estimate the number and biomass of pollock in the Eastern Bering Sea, which, as you can imagine, is a big undertaking. In order to complete this job, they use a lot of sophisticated technology to determine where the fish are as well as statistical methods to extrapolate the total number of fish from the samples taken. This job is extremely important as it helps to determine the health and sustainability of the pollock population in the Bering Sea so that the government can model and forecast next year’s population numbers, and the North Pacific Fishery Management Council can set future catch quotas.

The first piece of technology used is the underwater acoustics. Echosounders send an audible ping down into the water and measure how long it takes to bounce off of an object (like a pollock) and return to the surface. Using the known value of the speed of sound, this technology can create a picture of where the fish are below the boat. While the acoustics only show that there is an object the length of a fish below, the scientists use their knowledge of the regions pollock normally occupy, the depth they regularly swim at, as well as the shape and size of pollock aggregations to determine when they are seeing pollock versus other types of fish.

The picture of the fish below the water created by the underwater acoustics.

Once it is determined that there is likely a large school of pollock in the area, then the trawling nets are deployed to catch pollock. Once the nets are hauled in, the total catch is weighed and then a smaller sample is pulled to collect length and weight data to determine the sizes of fish in the area. Other samples, such as the pollock ear bone (otolith) or ovaries may also be taken at this time. Using statistics, the number and length of pollock in the entire catch and then in the entire area is estimated.

Trawling nets on the ship.

Personal Log:

The flight into Dutch Harbor was very exciting. Before boarding the plane, they weigh you and your carry-on baggage to make sure the plane will be balanced and that there is not too much weight. The airport at Dutch Harbor is not much more than a landing strip between two mountains. We came in for landing right over the water and for a second it looked like we might land on the water before the landing strip appeared. Once we reached the dock where we boarded the NOAA Ship Oscar Dyson, I saw a sea otter, but it disappeared before I could take a picture of it!

The sign at the Dutch Harbor airport. Notice the latitude and longitude; this is the farthest north I have ever been!

So far, I am adjusting to life at sea. The first day the boat was a little rough and I got a bit seasick, however after seeing the ship’s medic for some medication I am feeling much better. During our first full day at sea we had to practice safety drills, which are required within 24 hours of departing. Once they announce the drill, you have to grab your life jacket and survival suit from your stateroom and bring them to the assembly point on the deck. Then, we had to practice putting on the survival suit, which is sort of like a giant wet suit complete with a hood, lights and a manually-inflated flotation device.

The plane I flew on from Anchorage to Dutch Harbor.

The ship itself is like a small city; there are the residences, which are the staterooms where we sleep, the entertainment, which is the lounge where there is always a moving playing, and the restaurant, which is the mess hall where great food is served three times a day. However, this “city” runs and powers itself; all electricity and water must be made aboard the boat.

The hardest adjustment so far has been a temporal one. I am responsible for the 4am – 4pm shift in the fish lab, which means I must rise by 3:30am every day! I am normally not an early riser so this has been tough, but the rocking of the ship means that when I do go to bed I normally get a great night’s sleep!

Did You Know?

Scientists collect the ear bone, called the otolith, from pollock to determine their age. This bone grows in rings for each year, just like a tree!